Over the last two decades the industrial woven fabrics industry has experienced a substantial and continuing change from using natural raw materials (e.g., Jute, Sissal, Paper, etc.) to the use of polyolefins (e.g., Polypropylene, Polyethylene) for general industrial uses (e.g., packaging, tieing, binding, etc.) with Low-Medium Duty performance requirements. The competitive price and high, strength efficiency of polyolefins have caused this dominance to be sustained. In the medium-to-heavy duty application areas the relatively high strength and low fabric processing costs of polyolefins have made it even more difficult for natural raw materials to compete. This being particularly so in the heavy duty applications for which relatively large quantitites of natural raw materials and more costly weaving procedures, are required in order for them to comply with demanding performance requirements.
With the passage of time and experience, however, a number of the less desirable aspects of polyolefins have been observed (e.g., non-biodegradable, do not burn to ash, difficult to durably mark or brand, low frictional properties, etc.), and of more recent times, as price differentials between polyolefins and natural fibres narrow and are even eliminated, there is a marked tendency for industry to be more critical of the polyolefins and to seek alternative materials. Whilst natural fibres reasonably, adequately and economically service low-medium duty industrial fabric requirements up to about 100 kg. breaking load (per inch width of fabric), breaking loads in excess of this will be expensive to manufacture from 100% natural raw materials and difficult to market for reasons of price and weight, within a wide range of industries.
A specific application in which polyolefins have fallen from industrial favour, evidencing the need and preference for alternative materials, is that of wool packaging. Damaging contamination of wool by polyolefins occurs when yarns or slivers of materials are caused to be freed into the packaged wool mass as a result of packaging material rupture or by other means. Elongate slivers of polyolefins will draft along with wool fibres during textile processing, ultimately to contaminate woolen end products. As the polyolefins are not dyeable with wool dyes, the undyed slivers within yarns spun from contaminated wool are easily seen and cause serious downgrading of the wool yarns and fabrics woven from same.
Apart from natural and polyolefinic raw materials for general industrial fabric purposes we have but man-made and synthetic fibres. Whilst steel and carbon fibres and such like are available they are not considered to be for general industrial purposes. Though many of the man-made and synthetic fibres are of high strength with tenacity values up to and in excess of 8.0 gm./d.tex those with tenacity values over the range 1.5-4.0 gm./d.tex show high cost for strength. Though such materials will weave into fabrics of sufficient strength, fabric cover and stability for general industrial woven fabrics of 80-250 kg. breaking load, the fact that they are traded for mainly apparel end use rather than industrial applications largely excludes them from the latter for reasons of price and availability.
Better cost for strength relationships occur however with high tensile synthetic fibres of tenacity in excess of 4.0-5.0 gm./d.tex; fibres which have a greater industrial useage orientation than those in the lower tenacity ranges. Though the most available synthetic fibres in the greater than 4.0-5.0 gm./d.tex tenacity range will weave into fabrics of sufficient cover and stability for a wide range of industrial purposes, the weight of synthetic used in order to achieve same, provides however, for more strength than is generally required. To reduce the weight of synthetic raw materials in such fabrics, to be in better accord with lower breaking load requirements e.g., 80-250 kg./inch, thus achieving a more acceptable cost for required strength relationship, means to produce fabrics of inadequate cover, dimensional stability, etc. for a wide range of general industrial end-uses. Thus an objective of this invention was to combine a calculated amount of high tensile synthetic thread (sufficient to provide required strength yet minimize cost) with a natural material, of relatively low cost, in such a way as to render the composite product weavable into fabric providing good fabric cover and stability when woven and having many of the properties of natural materials. In order to sustain fabric cohesion and unity when in use e.g. under load, an important requirement is that the natural/synthetic composite performs as one and not as a mixture with for example the normally weaker natural material breaking down before the synthetic material. It was preferred that the performance of the natural material be upgraded by its incorporation within the composite, acting in unison with the stronger synthetic. A further objective of the invention was to combine both the synthetic and natural materials in such a form as to minimize production and fabrication costs.
To these ends the composite tapes of this invention have been produced to provide alternative material to those in present use, for weaving into industrial fabrics particularly for use, but not exclusively, within a breaking load range of 80-250 kg./in. width and for other uses in the form of high tensile tapes.